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This study was performed to examine the belt fit problem as it relates to various size vehicles, predict the additional seat belt length necessary to accommodate up to the 99th percentile person, and evaluate the safety aspects of additional belt length.

Ten vehicles that had been reported as having a belt fit problem were tested. Two were found to just meet the standard. Most had 6-7 inches of belt remaining even with the seat in the forward most position.

A series of vehicles were tested for belt length required as a function of occupant weight using ten subjects. It was determined that each additional inch of belting will increase the accommodated body weight by 7.5 pounds. Thus, to accommodate up to the 99th percentile person weighing 260 pounds or 45 pounds above the standard 95th percentile person requires an additional 6 inches of belt. It was also determined that the belt length gained by seat travel is 2-3 times the seat travel or about 15-17 inches of belt.

Six crash simulations were performed with the Hybrid III dummy at 30 mph in the passenger seat to evaluate the change in dynamics and excursions with additional belt lengths. Up to 10 inches of belt length above the minimum required were tested. It was found that the peak accelerations increased only nominally. The amount of belt spoolout increased from 1.6 to 3.0 Inches. The total excursion of the head of the dummy increased 3 inches from about 18 to 21 inches.